We have used a polymerase chain reaction method and nucleotide sequence analysis of the cloned PCR products to identify and characterize the VH, D and JH segments expressed in four EBV immortalized malignant B-cell lines, two of B-CLL origin and two of B-PLL origin. All four cell lines used VH3 family members with greater than 86% homology to reported VH3 sequences. However, only one of the cell lines used a described VH3 family germline gene with little or no somatic mutation. The VH segments utilized by the other three cell lines show less than 95.2% homology to already described VH3 family germline genes. This finding may be explained by somatic mutation and contradicts current accepted ideas about germline VH usage in B-CLL. D germlines used are : DXP1, DIR and D21/9; three use the JH4 gene and all have a variable number of N insertions. In the VH Ig assembly of these chronic B cell malignant cell lines, there seems to be neither preferential VH3 individual member gene usage or D germline gene usage, but there is suggestion of biased JH4 gene usage. Ontogenetically the VH Ig region gene usage in these EBV transformed B-CLL and B-PLL cell lines appear to be more adult-like than fetal.